I know that one can have a greater or lesser amount of surety (i.e. "I'm not really sure"), but don't you either know or not know something? Are there degrees of knowledge? I hear this phrase often from reporters and news correspondents: "We don't really know..." I think that this is a way to avoid saying "We don't know", which sounds more blunt, but is more precise.

  • 1
    I don't really know the answer to this question; I do know the answer to some, but I really don't know others at all. Commented Jun 13, 2011 at 20:20

5 Answers 5


Frequently, it is simply a matter of preference. However, the following variations could be interpreted slightly differently.

I don't know.

A simple declaration. Unambiguous.

I don't really know.

This is often used to deflect a negative self-assessment. It's common to not want to admit that we don't know something, so we occasionally de-emphasize the declaration.

I really don't know.

You didn't mention this variation, but this is often used to do the opposite, actually emphasizing the fact that we don't know. This can be used to stress to someone who may not believe you, that you in fact, really don't know something.

These are really just minor nuances, and the phrases are often used interchangeably. If someone wants to express a degree of knowledge, some other phrase is usually used in conjunction with the declaration. For example, "I don't know enough about X to answer that."

  • +1 for "It's common to not want to admit that we don't know something, so we occasionally de-emphasize the declaration." This is my point exactly. It just seems a little disingenuous.
    – Fred
    Commented Mar 5, 2011 at 4:40
  • 1
    To me this can be a perfectly acceptable and non-weaselly follow-up as in, "I have my ideas about that, but I don't really know." It's emphasizing that you may sort of know, but not solidly so.
    – ErikE
    Commented Jun 19, 2011 at 2:28

I don't really know suggests that the speaker may know a little about the subject discussed but not really that much.

For example,

I don't know Jimi

probably means you have never heard of Jimi, while

I don't really know Jimi

means you may have heard of or even met Jimi but you do not know much about him.

  • I understand your answer as it relates to broad topics. But here's a specific example of what I mean: "Are there currently backdoor talks between the administration and party leaders?" "We don't really know". My point is that one either knows or does not know such a specific fact.
    – Fred
    Commented Mar 5, 2011 at 4:24
  • Yes, thank you. I was not as specific as I should have been with the question.
    – Fred
    Commented Mar 5, 2011 at 4:43
  • 1
    @Fred: Even specific facts are open to ambiguity, inference, deduction, etc. Maybe you don't know for certain that there are talks, but you've heard rumours. In that case, it's perfectly fair to say you don't really know, even if you believe the rumours. Commented Mar 31, 2011 at 1:46

Different languages emphasize different things. Japanese, for example, has a tendency to emphasize the speaker's belief in the probability of events and the certainty of knowledge. The number of ways a Japanese speaker can say "I think it will rain tomorrow" is quite large.

English, in contrast, is very sensitive to order in which things occur or are likely to occur, as evidenced by such things as the future perfect tense (e.g., "by then I will have known the result).

But English also has a strong bias toward stress, so that degrees of knowledge are able to be pinpointed: I don't know. I'm not sure. I sort of know. I guess. Maybe. It's possible that... Etc.

  • Thanks for the insight into another language. I enjoy learning about the differences. To me, "I don't know" is clear; "I'm not sure" indicates ones lack of certainty; "I sort of know" is nearly as ambiguous (in my opinion) as "I don't really know"; "I guess" = "I don't know"; "Maybe" and "It's possible that" get at probability.
    – Fred
    Commented Mar 5, 2011 at 4:37

The word really used in this context is an all-purpose intensifier:

I really don't understand.

You're really getting on my nerves.

She really had me going there for a while.

In each of those cases the really could be dropped without a change of meaning, but the level of intensity of the statement would not be the same. The word fairly implores the listener to believe what is being said. It anticipates and attempts to preempt objections to a statement. In the normal course of a conversation, such an objection might be raised as the word itself.

John: I don't understand.

Joan: Really?

John: Yeah, really. I just don't get it.

By adding the really John would be attempting to avoid having to repeat himself.

  • Thank you for your answer, but I think that it refers to the phrase "I really don't know". I understand that this phrase emphatically asserts that one does not know. My question was about the phrase "I don't really know".
    – Fred
    Commented Mar 5, 2011 at 4:23
  • @Fred: That's all right. It is a parallel construction. Really operates the same way whatever the verb. That's all I'm saying.
    – Robusto
    Commented Mar 5, 2011 at 10:36
  • I think that's wrong. "I don't really know" is, most emphatically, not as strong as "I really don't know."
    – ErikE
    Commented Jun 19, 2011 at 2:36

To my mind, I'm not really sure, suggests that the speaker might not be certain of something, but they have some supporting evidence to think so. For example:

Why did he leave?

I don't really know. However, I suspect it had something to do with the waffles.

Rather than hedging on the side of not knowing something, it can be hedging in the other direction.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.